The invention relates to tomographic apparatus for producing transverse layer images of a radiography subject, having a radiation measuring arrangement which comprises a radiation source producing a radiation beam, penetrating the radiography subject, whose cross sectional extent perpendicular to the layer plane is equal to the thickness of the layer, and also a radiation receiver which determines the radiation intensity behind the subject, in which the measuring arrangement is arranged on a movable support which is displaceable in a plane parallel to the plane of the layer, and the support together with the measuring arrangement is rotatable by means of a rotating track, a motor being present for driving the rotating track for irradiating the radiography subject from different directions and for driving the support, and the apparatus having a measured value converter for transforming the signals supplied by the radiation receiver into a layer image.
A tomographic apparatus of this kind is described in the U.S. Pat. No. 3,986,031. In this apparatus belt and chain drives are provided between the drive motor and the rotating track and the support, these drives transmitting the rotary movement of the motor on the one hand to the rotating track and on the other to a crank gear with two crank wheels. The mechanical construction of this known apparatus is extremely complicated, and the apparatus is therefore expensive and prone to breakdowns.